JPH05240136A - Handheld power apparatus - Google Patents

Abstract

PURPOSE: To provide a power apparatus which can be operated smoothly without interruption. CONSTITUTION: An electric switch 6 is connected to an electronic control device 54 limiting the rotational speed of an internal combustion engine to a value that is insufficient to actuate a clutch. The electronic control device 54 is brought to a non-operation condition by closing the electric switch 6. Thus, even when the electric switch 6 is turned off, the internal combustion engine is not stopped by the electronic control device, but decelerated to a predetermined unloaded rotational speed. Therefore it is not necessary to restart the internal combustion engine, and operation can be conducted smoothly without interruption.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is operated by an engine, in which a tool driving unit is connected to the engine through a clutch which operates according to the engine speed. A power unit guided by hand, which has two grips for carrying and guiding the power unit by hand, and operating means attached to each of these two grips. The present invention relates to a manually guided power unit (for example, a chainsaw) which is operated to operate the power unit. 2. Description of the Related Art The casing of a power plant of this type is provided with two grips for carrying and guiding the power plant with both hands. One grip is arranged in the front area of the casing and is configured as a gripping curve. One operating means is attached to each of the grips,
The power unit is operated by operating both operating means at the same time, and this structure serves as a safety device for preventing an accident of an operator. Therefore, if one of the operating means is not operated, the power unit is stopped. A safety device of this kind (US Pat. No. 3,313,12)
No. 77), one of two short-circuiting switches is arranged on each of the web and the curved leg of the front gripping curved body. Therefore, each switch is associated with the working state of the power plant. When both switches are free, a short circuit occurs which shuts down the power plant. Therefore,
Each time the front grip is released, the power plant has to be started anew and the work with the power plant has to be interrupted each time. SUMMARY OF THE INVENTION An object of the present invention is to provide a power plant which can be smoothly operated without interruption. In the present invention, in order to solve the above-mentioned problems, the operating means attached to one of the two grips is constructed as an electric switch,
The electrical switch is connected to an electronic control device which limits the engine speed to a value which is insufficient for the response of the clutch, and the electronic control device is activated by closing the electrical switch. It is brought into an operating state. Embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view of a chainsaw as a power unit. The chain saw guided by hand has a casing 1 to which a front grip 2 and a rear grip 3 are fixed. The saw chain, not shown, is normally guided on the chain track 4. The rear grip 3 which is held by the right hand during driving has a diaphragm lever 5 and a locking lever 5A as operating means. The locking lever 5A must be operated simultaneously with the throttle lever 5 to start the internal combustion engine. Such an arrangement is commonly used and therefore need not be described in detail. The front grip 2 is curved and has, above the casing 1, a grip portion 2a lying laterally to the chain track 4. The gripping curved body 2 is
By its end, it is connected to the casing 1 via a vibration buffering element such as a rubber buffer or a vibration-proof metal piece. The front grip 2 constructed as a gripping curved body is provided with a switch 6 as an operating means. The switch 6 is connected to an electronic control unit of an ignition circuit of an internal combustion engine, as will be described later. Switch 6 is generally
It extends over the entire length of the front grip portion 2a and over the entire length of the lateral curved portion which is not visible in the plan view of FIG. The operator grips the front grip 2 and thus the switch 6 with his left hand, regardless of whether he grips the front grip portion 2a or the lateral grip portion which is not visible in FIG. FIG. 2 shows an example of the switch 6. The switch 6 has two strip-shaped spring-elastic contact strips 7 and 8 which are spaced substantially parallel to each other by a spacing piece 6b. The spacing pieces 6b are arranged evenly distributed over the entire length of the contact strips 7, 8 and consist of a rubber-elastic insulating material, for example polyurethane foam. The contact strips 7 and 8 and the spacing piece 6b are both surrounded by an insulating cover 6a. This insulating cover 6a is likewise made of an elastic material, for example of rubber or an elastically deformable synthetic material which allows mutual pressing of the two contact strips 7 and 8 up to the contact point. The insulating cover can be provided integrally in the cover of the front grip 2 by, for example, foam encapsulation, while it can also be glued onto the front grip 2. Suitably, the entire switch 6 may be removably secured to the front grip, for example by a clamp or clip. Connected to the two contact strips 7 and 8 is one of the two conductors 50 or 51, which are guided inside the insulating cover 6a by points 52A and 52B into the casing by a lead-in piece 52, respectively. There is. When the front grip 2 is not gripped by hand, the contact strips 7 and 8 are in the rest state shown in FIG. 2, i.e. not in contact with each other. The switch 6 is then in the shut-off position. When the front grip 2 is held at any position in the region of the gripping curve leg of the grip part 2a or laterally, the contact strips 7 and 8 are obtained.
Are elastically deformed in the region between the insulating spacing pieces 6b, so that the contact strips come into contact with each other and the switch 6 closes. When the front grip 2 is loosened, and thus the switch 6 is loosened, the two contact strips 7 and 8 are elastically separated from one another. The chainsaw is held by the grip portion 2a, for example for cutting thick branches. Chain track part 4
When operating in a horizontal state, for example, to tilt a tree, it is held by a rectangular gripping curved body portion that extends perpendicularly to the grip portion 2a. In any working state, the switch 6 is forcibly operated by grasping the front grip 2. In the embodiment of FIGS. 3 and 4, the switch 6'is
Are mounted in a vibration damping element 14 which is embodied as a vibration isolating metal. The vibration damping element 14 has a rubber elastic body 15 having a substantially cylindrical shape. The rubber elastic body 15 has both end surfaces 1
In 6 and 17, they are fixed to each metal plate 18 or 19 by sulfuric acid treatment. By means of these metal plates 18, 19, the element 14 is fixed in the casing 1 or at the associated end of the grip 2. One of the fixing screws forms the contact of the switch 6 '. The washer 21 of the screw 20 has a conductor 2
2 is connected. The fixing screw 20 has its free end 23
Project into the hollow space of the rubber elastic body 15 and are surrounded there by a contact strip 24 which is triangular in cross section. This contact strip 24 forms the counter contact for the fixing screw 20 and surrounds the threaded end 23 with play when the front grip 2 is not loaded by the weight of the chainsaw. The contact strip 24 includes:
A conductor 24a leading to the electric motor is connected. As shown in FIGS. 3 and 4, the contact strip 24
Are inserted by their corners into an annular groove 26 formed in the inner wall of the rubber elastic body 15, so that the contact strip 24 moves and vibrates in the axial direction of the vibration damping element 14. Rotation of the mitigation element 14 about its axis is prevented. When the operator grips the front grip 2 and lifts the chain saw (the lifting direction is the upward direction in FIG. 3), the weight of the chainsaw (the direction in which the weight acts is the downward direction in FIG. 3) causes the metal plates 18 and 19 to move.
Are displaced in parallel in opposite directions, and as a result, both metal plates 1
The rubber elastic body 15 held between 8 and 19 deforms laterally with respect to its longitudinal axis. At that time, the fixing screw 20 and the contact strip 24 contact each other, and the switch 6'is closed. In the embodiment of FIG. 5, the front grip 2'comprises a metal tube 35 with a sheath 34, inside the sheath 34 of the tube 35 two switches 36 and 36 'are arranged. There is. The covering 34 is made of an elastic insulating material such as rubber and has two ridges 40 and 40 'which are diametrically opposed to each other. These ridges extend beyond the central grip portion and the lateral grip portion and thus extend over the entire area where the grip can be gripped by hand. Both switches 36 or 36 'are embedded in these ridges. Switch 36 or 36 '
Are formed corresponding to FIG. 3 and are thus respectively spaced apart from each other by two spring-elastic contact strips 3.
7 and 38 or 37 'and 38'. Grooves 39 or 39 'are provided in both ridges 40 and 40', respectively, for embedding both switches. The material of the covering 34 is so flexible that the contacts can be closed by pressing on the ridges. Both switches are electrically connected in series. By arranging both switches on opposite sides on the diameter of the grip, it is ensured that the circuit is closed only when the user's hand tightens the grip. In the embodiment of FIGS. 6 and 7, the front grip 2 "likewise comprises a metal tube 35 which is surrounded by a covering 45. This covering 45 likewise comprises the front grip 2". A ridge 53 is provided which extends over the entire hand-grassable area. The contact strip 43 of the switch 41 is inserted in the groove 44 of the raised portion 53. The opposite contact is formed by the metal tube 35 which constitutes the grip 2 ″. Therefore, the groove 44 opens in the direction of the metal tube 35, so that the rib 46 of the contact strip 43 is
The corresponding recess 47 can be penetrated and the ridge 5
The metal pipe 35 can be contacted when a sufficiently large pressure acts on the metal pipe 3. The advantage of this embodiment is that the contact piece 4
3 can be easily pushed into the groove 44. Instead of the rib-like projections that penetrate through it, the contact strips 43 can also have several nodes, etc., which are arranged at a distance in front of and behind one another in the axial direction of the contact strips. FIG. 8 is a configuration diagram in which the switch 6 is connected to the electronic control unit 54 of the ignition circuit for the internal combustion engine. The switch 5 is a diaphragm lever (not shown here). The electronic control unit 54 acts as a rotational speed limiting device when the switch 6 is open, and therefore when the front grip 2 is not tightened by the operator. The engine speed is then limited so that it is not sufficient to connect the drive of the saw chain to the engine shaft. A centrifugal clutch is arranged between the engine shaft and the drive part of the saw chain, which causes a frictional connection to the drive part only when the engine speed reaches a certain value. The electronic control unit 54 is provided with an ignition coil 58 which operates in normal operation and is supplied with a pulse-wave-shaped ignition voltage via the connection terminal ZS. A control circuit 57 is connected in parallel with the ignition coil, and the control circuit 57 is connected.
Operates to bridge the ignition coil 58 in its shunt state while its switch is on, and thus short the ignition voltage. It is also possible to form the control circuit 57 as follows, that is to say periodically to suppress several consecutive pulses each time. In that case, if the control circuit is operating, the pulse per unit time of the ignition coil is only a pulse corresponding to a predetermined rotation speed, for example, 3000 rotations / minute. The electronic control unit 54 has a revolution speed measuring device 61 for measuring the revolution speed of the engine and sending a signal corresponding to the revolution speed to a comparator 55 connected next. The comparator is provided with a fixed reference value corresponding to a predetermined rotation speed of 3000 rpm, for example. If the actual value of the measured speed is equal to or greater than the reference value, the comparator sends a signal to the electronic switch 56, which turns on the electronic switch at the threshold value and activates the control circuit 57. To do. If the control circuit 57 is formed merely as a shunt for the ignition coil 58, the components 61, 55, 56, 57 form a regulating circuit. That is, when the engine speed exceeds the reference value, the ignition voltage is short-circuited, and after the switch is turned off, if the engine speed drops below the reference value, the short circuit stops,
As a result, ignition occurs again and the number of revolutions increases again. Therefore, this adjusting circuit operates as an on / off adjusting device. On the other hand, when the control circuit 57 periodically suppresses the pulse, the engine speed is kept constant at a predetermined value as long as the control circuit 57 is switched on.
The electronic switch 56 has a second input, which can be grounded via the control line 59, whereby the switch 56 is cut off and the control circuit 57 can no longer be activated. On the control line 59 there is a switch 6 which closes when the chainsaw is held by the front grip 2, as already explained. Therefore, by closing the switch 6, the adjusting circuits 61, 55, 56, 57 are shut off, or the operation of the control circuit 57 is stopped, and as a result, the engine speed is raised to the operating value and the saw clutch is passed through the centrifugal clutch. The drive of the chain is switched on. Instead of switch 6, it is of course possible to use switch 6 '(FIGS. 3 and 4) or switch 41 (FIG. 7) or combination switch 36, 36' (FIG. 5). When the operator releases the front grip 2 during the work with the chainsaw, or the reaction (kickback) occurs.
If the operator's hand slips off the front grip 2 due to the reason, the switch 6 is opened and the adjustment or control is immediately performed, so that the engine speed reaches a threshold value, for example, 3 degrees.
It goes down to 000 times / min and the centrifugal clutch switches off the drive of the saw chain. At that time, the engine is not stopped, and the front grip 2 only needs to be newly gripped in order to maintain a predetermined unloaded rotation speed corresponding to the threshold value, so that the chain saw is used for further work. In the event of danger, the short-circuit switch 60 can be used to completely short-circuit the ignition voltage in a known manner, thus stopping the engine. According to the present invention, when the electric switch as the operating means attached to the grip is turned off, the rotation speed of the internal combustion engine is reduced to a threshold value (for example, 3000 times / minute) by the electronic control unit. ) Down, clutch disengages power tool tool drive. At that time, the internal combustion engine is not stopped and maintains a predetermined no-load rotation speed, so that the operation can be smoothly performed without the trouble of restarting the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a power plant according to the present invention. FIG. 2 is a first embodiment of an electric switch as an operating means. FIG. 3 is a cross-sectional view of a second embodiment of the electric switch. FIG. 4 is a sectional view taken along line IV-IV in FIG. FIG. 5 is a cross-sectional view of a third embodiment of an electric switch. FIG. 6 is a cross-sectional view of a fourth embodiment of an electric switch. FIG. 7 is an enlarged view of a portion A of FIG. FIG. 8 is a configuration diagram of an electronic control device that controls the rotation speed of the internal combustion engine in conjunction with an electric switch. [Explanation of Codes] 6 Electric Switch 54 Electronic Control Device 55 Comparator 56 Electronic Switch 57 Control Circuit 58 Ignition Coil 59 Control Line 60 Short Circuit Switch 61 Rotational Speed Measuring Device

Claims (1)

Claims: (1) A tool drive unit operated by an internal combustion engine,
A manually guided power plant connected to an internal combustion engine via a clutch that operates according to the rotational speed of the internal combustion engine, the two grips (2, 2) for carrying and guiding the power plant by hand. 3) and operating means (5 or 6) attached to each of these two grips (2, 3), so that the power unit is operated by operating both operating means (5, 6). In the manually guided power plant, the one grip (2) of the two grips (2, 3)
The operating means (6) attached to the electronic device is configured as an electrical switch, and the electrical switch (6) limits the rotational speed of the internal combustion engine to a value such that the clutch response is insufficient. Guided by hand, characterized in that it is connected to the control device (54) and that the electronic control device (54) is brought into the inactive state by closing the electrical switch (6). Power plant. (2) A rotation speed adjusting device in which the electronic control device (54) includes an electronic threshold value switch (55, 56) that determines whether to introduce the adjustment of the rotation speed of the engine depending on a predetermined minimum rotation speed of the engine. The power plant according to claim 1, which has (55, 56, 57, 61). (3) The electronic control unit (54) has a control circuit (57) attached to the ignition coil (58) of the engine, and this control circuit (57) causes the engine speed to reach a predetermined reference value. The power plant according to claim 1 or 2, wherein the post-ignition pulse is periodically suppressed. (4) The electronic control unit (54) has a control circuit (57) attached to the ignition coil (58) of the engine, and this control circuit (57) causes the engine speed to reach a predetermined reference value. After that, the ignition pulse is suppressed until the rotational speed falls below the reference value.
The power plant according to item 2 or item 3.